Detailed explanation of position in CSS (code example)

The content of this article is to share with you a detailed explanation (code example) about position in CSS. Friends in need can refer to it. I hope it will be helpful to you.

CSS position property is versatile and powerful. It allows setting or changing the position of an element. It has 4 possible values: static (default), relative, absolute, fixed. (Recommended course: css video tutorial)

It is usually used with 4 coordinate attributes: left, right, top, bottom

static

This is the default position value: static elements only follow natural flow. They are not affected by any left, right, top or bottom values.

relative

When position is set to relative, the element can move based on its current position.

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The effect is as follows:

Let us continue to look at it:

p{ border: 1px solid blue;}

The effect is as follows:

The red border is moved 20 pixels from the left and 10 pixels from the top, relative to its natural position, where it should be.

Note that the blue paragraph has not moved at all. By using relative positioning, the red paragraph can be moved freely without breaking the layout. The only thing that's inappropriate is that all other elements except itself don't know that the element has moved.

absolute

When position is set to absolute, elements can move based on the first positioned element.

"Positioning? What is a positioned element?"

A positioned element is a position whose value is relative, absolute, or fixed. Therefore, an element is positioned unless the position is unset or static.

The characteristic of a positioned element is that it can serve as a reference point for its child elements.

Let us imagine a simple hierarchy:

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p{ border: 1px solid blue;}
.second{ position: relative;border:1px solid red; left: 20px; top: 10px;}

The effect is as follows:

The height of the yellow part is 200px, and its position is set is relative, converts it into the reference point for all child elements.

When the position of the green paragraph is set to absolute, it can move freely according to the yellow part. By setting the bottom and left values, it will move to the lower left corner.

What happens if we set left and right?

If width is not set, applying left: 0 and right: 0 will stretch the element across the entire width. It is equivalent to setting left: 0 and width: 100%.

If width is set, right discards the value.

fixed

When position is set to fixed, it works like absolute positioning: you can set left/right and top/bottom coordinates.

The only difference is that the reference point is the viewport. This means that the fixed element does not scroll with the page; it remains fixed to the screen.

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